The present invention relates generally to a method and apparatus for setting a viewpoint and a line of sight in a three-dimensional image constructing method, and more particularly to a method and apparatus for setting a viewpoint and a line of sight that are parameters required for constructing a three-dimensional image (3D image) in a central projection method.
In the central projection method, a viewpoint is not a plane but a point, and a three-dimensional image existing between the viewpoint and a predetermined projection plane (a plane perpendicular to a line of sight) is projected on the projection plane with the viewpoint being an origin. The central projection method is suitable for obtaining the projected images that represent the endoscopic views of the interior of a blood vessel, a bronchial tube, etc. (refer to Japanese Patent Provisional Publication No. 8-16813). In the central projection method, the projected images that simulate the endoscopic movement can be obtained by properly updating the viewpoints and the lines of sight.
When the viewpoint is moved within the interior of a tube-like substance in the direction of the depth, the next viewpoint and line of sight (an angle of the projection plane) are properly set with reference to a display screen of a pseudo three-dimensional image created by the central projection method to thereby sequentially update the display screen (refer to Japanese Patent Application No. 7-231496).
An operator, however, observes the pseudo three-dimensional image, which is projected on the projection plane that is the two-dimensional plane, while setting the viewpoint and the line of sight within the pseudo three-dimensional image. For this, reason, the operator has no information about the depth in the pseudo three-dimensional image, and the operator must set the viewpoint and the line of sight after repeated trial and error in order to obtain a desired pseudo three-dimensional image. Thus, it is inefficient and takes a long time to set the viewpoint. The three-dimensional image created in the central projection method has a disadvantage in that when a display screen shows the inner wall of a blood vessel, it is difficult to recognize which blood vessel of a subject is shown. Moreover, the viewpoint strays out from the interior of the tube-like substance and enters into or over the wall when the moving distance of the viewpoint is too long. It is thus difficult to obtain the desired pseudo three-dimensional image after the movement of the viewpoint.
The present invention has been developed in view of the above-described circumstances, and has as its object the provision of a method and apparatus for setting a viewpoint and a line of sight in a three-dimensional image constructing method wherein it is easy to recognize and set the viewpoint that is used to create a pseudo three-dimensional image if an object region of a subject be endoscopically observed from inside, the viewpoint can be set in a short period of time, and the desired pseudo three-dimensional image can be obtained after the movement of the viewpoint.
To achieve the above-mentioned object, the present invention is directed to a device for setting a viewpoint and a line of sight, in a three-dimensional image constructing method including setting means for setting a viewpoint and a line of sight from the viewpoint in a stacked three-dimensional image formed by stacking a plurality of tomographic images including a volume image, the three-dimensional image constructing method comprising the steps of: shading and projecting the three-dimensional image on a projection plane perpendicular to the line of sight by using a central projection method in which an origin is the viewpoint set by the setting means; and displaying a projected image on a monitor screen as a pseudo three-dimensional image, wherein: the setting means for setting the viewpoint and the line of sight comprises: a primarily-setting means for primarily settng the viewpoint and the line of sight; an image constructing means for cnstructing a first sectional image formed by slicing the three-dimensional image with a first plane including the primarily-set viewpoint and line of sight, and displaying the first sectional image on the monitor screen; and a marker display means for displaying a marker indicating the primarily set viewpoint and line of sight on the plane including the first sectional image in accordance with the primarily-set viewpoint and line of sight.
According to the present invention, the primarily-setting means primarily-sets the viewpoint and the line of sight, and the image constructing means constructs the first sectional image that is formed by slicing the three-dimensional image with the first plane including the primarily-set viewpoint and line of sight and displays the first sectional image on the monitor screen. The marker display means displays the marker indicating the viewpoint and the line of sight on the plane including the first sectional image.
It is therefore easy to recognize and set the viewpoint and the line of sight for the pseudo three-dimensional image that is shown on the monitor screen.
By outputting an instruction to move the position and direction of the marker, and moving the marker on the plane including the first sectional image and updating the viewpoint and the line of sight in accordance with the instruction, it is easy to set the viewpoint and the line of sight, and the viewpoint and the line of sight can be set in a short period of time.